c# - C# 中的乘法错误

Question

当乘以一组 int 并将结果转换为 long 时，我得到的答案与我乘以一组 double 并将结果转换为 long 时不同。例如:

int a = 5;
int b = 5;
int c = 7;
int d = 6;
int ee = 6;
int f = 8;
int g = 9;
int h = 6;
int i = 6;
int j = 4;
int k = 8;
int l = 9;
int m = 5;
long x = a * b * c * d * ee * f * g * h * i * j * k * l * m;

double aa = 5;
double ab = 5;
double ac = 7;
double ad = 6;
double aee = 6;
double af = 8;
double ag = 9;
double ah = 6;
double ai = 6;
double aj = 4;
double ak = 8;
double al = 9;
double am = 5;
long y = (long)(aa * ab * ac * ad * aee * af * ag * ah * ai * aj * ak * al * am);

谁能告诉我为什么会这样？谢谢

Answer 1

你遇到了一个整数溢出，因为每当你将两个 int 相乘时你就会得到 int:到目前为止，这被解释为 Int32

 a * b * c * d * ee * f * g * h * i * j * k * l * m

并且只转换为Int64 (long)。要更正实现，请声明所有变量最初都是 long 例如

  long a = 5;
  long b = 5; // actually, not necessary, since a * b will be long, but safer
  long c = 7;
  ...
  long m = 5;

  long x = a * b * c * d * ee * f * g * h * i * j * k * l * m;